The present invention relates to bathtubs in which air is bubbled into the water, and in particular to air delivery systems for such bathtubs.
Therapeutic water baths and pools are well-known. Spas or whirlpool tubs are common examples in which water streams from jets through the walls of the basin flow into the water beneath the surface, usually directed at muscle areas of a person's body, for example shoulders, back and thighs. The force from the jets “massage” the bather directly, as well as agitate the water, to provide therapeutic effects for other parts of the body not directly in the path of the jets. U.S. Pat. No. 6,185,757 discloses one such bath with water jets.
Some tubs instead use air streams to agitate the water. U.S. Pat. Nos. 5,898,958 and 6,317,903 each disclose a tub that introduces air into the water from a blower or air pump passed through conduits and a manifold to air jets in the walls of the tub. The air delivery systems in these patents are rather complex and may require a separate conduit for each air jet.
Co-pending and co-owned U.S. patent application Ser. No. 10/774,123, filed on Feb. 6, 2004, the disclosure of which is hereby incorporated by reference, discloses an air bath with an improved air distribution system that alleviates dead zones (or non-air infused pockets of water in the tub) to more consistently achieve full body treatment. That system helps overcome a problem of the air jets, particularly those farthest from the blower, becoming blocked by the pressure head of the water in the tub, particularly when the blower speed is decreased. The air jets are arranged in rows that extend essentially around the entire perimeter of the basin. The rows of air jets are spaced apart vertically so that the air jets in each row realize a different pressure head, the vertically higher the air jets, the less the pressure head. Thus, when the water level is high and/or the blower is running at a low speed such that the air jets in the lower rows become effectively blocked, air can still flow through the air jets in the higher row(s), thereby maintaining bubbling around the entire perimeter of the basin.
If all the air jets were to become blocked and stay blocked long enough, back pressure could build up sufficient to stall the blower. Heat or current limiting circuitry would have to be provided to shut down the blower motor to keep it from being damaged. A damaged blower motor would render the air system inoperable, and replacement motors are expensive, and typically require a service call from a technician, further adding to the cost. Even if damage to the motor could be avoided, it may still disrupt operation of the bubbling and destroy the air bath.
The system described in the aforementioned patent application helps protect the blower to some extent by keeping open an outlet for the air flow from the blower. However, to avoid even the uppermost air jets from becoming blocked, the blower must be selected and operated at sufficiently high speeds to overcome the pressure head. This somewhat limits the ability to provide soft, low density bubbling, without the use of supplemental tanks or accumulators, as described in U.S. Pat. No. 4,907,305.
U.S. published application 2003/0233704 discloses a bathtub with an air distribution system that can have a pressure relief valve upstream from the air jets to relieve excess pressure from the blower and prevent it from overheating. Thus, this system requires valving that opens in the event of an excess pressure situation to protect the blower motor. And, since this is merely a protective measure, the system does not provide for more subtle bubbling.
Hence, a need exists for bubble tubs improved relative to these deficiencies.